Fox News host Bill O'Reilly says a plethora of celebrities are endorsing socialist Bernie Sanders for the Democratic presidential nomination and has challenged one of them, comic actor Will Ferrell, to a debate.

"Do you think Will Farrell knows anything?" O'Reilly said. "I'll debate you any time, you pinhead."

O'Reilly said he would take Ferrell on about Sanders, politics in general or his films.

Later on his own show, "The O'Reilly Factor," the host admitted his challenge was "obnoxious" and said, "I shouldn't have called out Will Ferrell, but I am getting a little fed up with these people."

While celebrities are free to support Sanders, O'Reilly said, Ferrell and others likely have no idea what the candidate really stands for and would never accept his debate challenge.

"He's a coward," O'Reilly regular Bernard McGuirk said.

Guest Greg Gutfeld said celebrities suffer from "stunted intellectual growth." They think people like them only because they like to "pretend" when acting, and they want to be taken seriously as thinkers.

Fox News host Bill O'Reilly says a plethora of celebrities are endorsing socialist Bernie Sanders for the Democratic presidential nomination and has challenged one of them, comic actor Will Ferrell, to a debate.